1. Field of the Invention
This invention relates to a wafer test system having integrated calibration apparatus and, more particularly, to a test system for measuring the thickness of thin films on silicon wafers which system includes at least one calibration chip having surface characteristics suitable for use in calibrating the apparatus.
2. Prior Art
Disclosed in U.S. Pat. 3,751,643 -- Dill et al. is a spectrophotometer suitable for use in measuring the thickness of thin films deposited on a substrate such as one made of silicon. In the course of operation of the system, it is necessary to calibrate the system by using a standard or sample having known transmission or reflective characteristics where the sample may be of bare silicon. In accordance with the prior art, the sample would be of substantially the same size as that of the wafers to be tested and would first be placed in position relative to the test probe. The calibration measurements are made, and thereafter test wafers can be placed next to the test probe.